The present invention relates to a novel supported polymerisation catalyst composition comprising a discrete metal complex, a support and an activator in particular an activator based on a Lewis acid, to a supported catalyst additionally comprising a Ziegler catalyst component and in particular to a method of preparing said supported catalyst.
The use of discrete metal complex based olefin polymerisation catalysts is well-known. Examples of such catalysts include metallocene complexes comprising a bis(cyclopentadienyl) zirconium complex for example bis(cyclopentadienyl) zirconium dichloride or bis(tetramethylcyclopentadienyl) zirconium dichloride disclosed in EP 129368, EP 206794, and EP 260130.
In such catalyst systems the discrete metal complex is used in the presence of a suitable activator. The activators most suitably used with such metal complexes are aluminoxanes, most suitably methyl aluminoxane or MAO. Other suitable activators are perfluorinated boron compounds.
It would however be beneficial to be able to use simpler and less costly activators with these discrete metal complexes.
WO 98/11144 describes catalyst systems based on discrete metal complexes comprising hetero-atom containing chelating ligands together with Lewis acids. Such systems have the advantage of not requiring the use of expensive aluminoxanes as activators. The aforementioned WO 98/11144 discloses that the discrete metal complexes may be supported and may also be used in the presence of Ziegler catalyst components. However there are no teachings of how such supported catalyst systems may be prepared.
We have now found that such supported catalyst systems based on discrete metal complexes which are suitable for the polymerisation of olefins and which do not require aluminoxane activators may be prepared by a specific preparative route which results in the metal complex being predominently fixed on the support.
Thus according to the present invention there is provided a method for preparing a supported catalyst composition suitable for the polymerisation of olefins said method comprising the steps of
(a) optionally pretreating a support,
(b) preparing a mixture of a neutral discrete metal complex and activator in a suitable solvent,
(c) contacting the support with the mixture from step (b), and
(d) removing the solvent to yield a free flowing powder, wherein the metal complex of step (b) has the formula.
(L)pMYnXmZq
where
L represents a ligand which remains attached to the metal under polymerisation conditions,
M is a Group IIIA element or Group IIIB, IVB, VB, VIB or VIII transition metal
Y is halogen or a group containing at least one O, S, N or P atom bound directly to M
X may be the same as Y or different and is chosen from halogen, a group containing at least one O, S, N or P atom bound directly to M, hydrogen or hydrocarbyl
Z is a neutral Lewis base
n greater than or=1
p greater than or=1
m greater than or=0
q greater than or=0.
The support may be for example organic polymer, functionalised organic polymers, polysiloxanes, functionalised polysiloxanes, ion-exchange resins and porous inorganic metal oxides and chlorides for example silica, alumina or magnesium chloride.
The preferred support is silica, in particular dehydrated silica. The inorganic metal oxides and chloride supports may be dehydrated by conventional methods for example by calcination at elevated temperatures. Water may be removed from supports that are unstable to elevated temperatures by Dean and Stark separation. The dehydrated support material may optionally be pretreated with a Group I-III metal alkyl compound for example by heating in a suitable solvent such as toluene. Particularly preferred compound are those comprising alkyl groups having greater than 2 carbon atoms for example trisiobutylaluminium.
The supported catalyst composition according to the present invention may be subsequently treated with an alkylating agent prior to the use as a polymerisation catalyst. A suitable alkylating agent is triisobutylaluminium.
It is a particular advantage of the present invention that the catalyst is not dissolved off the support in solvents normally used in polymerisation systems eg. alkanes, aromatics. In this way the metal complex is predominantly fixed to the support.
Particularly suitable complexes of the present invention are those having the general formula:
(L)pMYnXmZq
where
L represents an unsubstituted or substituted cyclopentadienyl ligand,
M is a Group IVB, VB, VIB or VIII transition metal
Y is halogen or a group containing at least one O, S, N or P atom bound directly to M
X may be the same as Y or different and is chosen from halogen, a group containing at least one O, S, N or P atom bound directly to M, hydrogen or hydrocarbyl
Z is a neutral Lewis base
n greater than or=1
p greater than or=1
m greater than or=0
q greater than or=0.
Suitable metal complexes include metallocene complexes comprising bis(cyclopentadienyl) complexes such as those disclosed for example in EP 129368 or EP 206794.
Also suitable for use in the present invention are complexes having constrained geometry such as those disclosed in EP 416815 or EP 420436.
For example complexes having the following general formula may be suitable: 
wherein:
Cp* is a single xcex75-cyclopentadienyl or xcex75-substituted cyclopentadienyl group optionally covalently bonded to M through xe2x80x94Zxe2x80x94Pxe2x80x94 and corresponding to the formula: 
wherein
R each occurrence is hydrogen or a moiety selected from halogen, alkyl, aryl, haloalkyl, alkoxy, aryloxy, silyl groups, and combinations thereof of up to 20 non-hydrogen atoms, or two or more R groups together form a fused ring system;
M is zirconium, titanium or hafnium bound in an xcex75 bonding mode to the cyclopentadienyl or substituted cyclopentadienyl group and is in a valency state of +3 or +4.
X each occurrence is hydride or a moiety selected from halo, alkyl, aryl, silyl, germyl, aryloxy, alkoxy, amide, siloxy, and combinations thereof (e.g. haloalkyl, haloaryl, halosilyl, alkaryl, aralkyl, silylalkyl, aryloxyaryl, and alkyoxyalkyl, amidoalkyl, amidoaryl) having up to 20 non-hydrogen atoms, and neutral Lewis base ligands having up to 20 non-hydrogen atoms;
n and m may be 0, 1 or 2.
Z is a divalent moiety comprising oxygen, boron, or a member of Group IVA of the Periodic Table of the Elements;
P is a linking group covalently bonded to the metal comprising nitrogen, phosphorus, oxygen or sulfur, or optionally Z and P together form a fused ring system.
The Y group has the same definition as above.
Illustrative but non-limiting examples of particularly suitable metal complexes for use in the catalyst composition of the present invention are those having the following Y groups in the above general formulae:
Halide
Trifluoromethanesulfonate
Methanesulfonate
Perchlorate
Fluorosulfonate
Nitrate
Pentafluorotellurate
Toluenesulfonates including halo substituted
Benzenesulfonates including halo substituted
Alkoxides
Aryloxides
HC(SO2CF3)2xe2x80x94
Oxalate and substituted oxalate
Acetate
Carboxylate
Acetylacetonate and substituted acetylacetonate
dithioacetylacetonate
Carbamate
Thiocarboxylate
Dithiocarboxylate
Thiocarbamate
Dithiocarbamate
Xanthate
Thioxanthate
Phosphinate
Thiophosphinate
Dithiophosphinate
dialkyldithiophosphate
amidinate
sulphurdiiminate
amidate
tropolonate
oxalate ester
nitrite
sulphinate
fluorosulphate
hydroxamate
thiohydroxamate
dithiohydroxamate
The preferred metal complexes are those in which the Y group is trifluoromethanesulfonate and in which X is the same as Y.
Preferred complexes are those in which M is zirconium, titanium or hafnium.
Suitable activators for use in the method of the present invention are Lewis acids.
Examples of suitable Lewis acids are alkyl aluminium compounds eg trimethyl aluminium, triisobutylaluminium, aryl aluminium compounds eg tris(pentafluorophenyl)aluminium, aluminium hydrides eg aluminium trihydride and mixed hydride/arylalkyl aluminium compounds eg di-isobutyl aluminium hydride, mono(pentafluorophenyl)di-isobutylaluminium. Also suitable are dialkyl aluminium halides eg dimethyl aluminium chloride or alkyl aluminium dihalides eg methyl aluminium dichloride or ethyl aluminium dichloride.
Alkyl or aryl borons eg 1,8 naphthalenediylbis(diisobutylborane), boron halides or hydrides, macrocyclic boron compounds eg boracyclododecane, alkyl magnesiums or magnesium halides are also suitable. Particularly suitable is tris(pentafluorophenyl) boron.
Aryloxy aluminium compounds eg (2,7-dimethyl-1,8-biphenylenedioxy)bis(di-iso-butylaluminium) and aryloxy boron compounds eg catecholborane are also suitable.
Suitable solvents for use in the method of the present invention include alkanes or aromatics. A particularly suitable solvent is toluene.
The catalyst system according to the present invention may also comprise a second catalyst component in particular a Ziegler catalyst component.
Thus according to another aspect of the present invention there is provided a method for preparing a supported catalyst suitable for the polymerisation of olefins comprising:
(a) impregnating a support with a first catalyst component (A), optionally further treating with a Group I-III metal alkyl compound,
(b) preparing a mixture of a second catalyst component (B) comprising a metal complex as herein before described and activator in a suitable solvent, and
(c) contacting the treated support from (a) with the mixture from (b), and
(d) removing the solvent to yield a free flowing powder.
The polymerisation catalyst component (A) may be a metallocene or may be a Ziegler catalyst component.
The Ziegler component of the catalyst composition of the present invention may be any Ziegler catalyst well known in the art but is preferred to be a catalyst comprising essentially atoms of titanium, magnesium and halogen.
The present invention also provides a process for the production of polyolefins, in particular homopolymers of ethylene and copolymers of ethylene with minor amounts of at least one C3 to C10, preferably C3 to C8 alpha-olefin. The process comprises contacting the monomer or monomers, optionally in the presence of hydrogen, with a catalyst composition prepared according to the method of the present invention at a temperature and pressure sufficient to initiate the polymerisation reaction.
Suitably the alpha olefin may be propylene, butene-1, hexene-1, 4-methyl pentene-1 and octene-1.
The olefin polymerisation catalyst compositions prepared according to the present invention may be used to produce polymers using solution polymerisation, slurry polymerisation or gas phase polymerisation techniques. Methods and apparatus for effecting such polymerisation reactions are well known and described in, for example, Encyclopaedia of Polymer Science and Engineering published by John Wiley and Sons, 1987, Volume 7, pages 480 to 488 and 1988, Volume 12, pages 504 to 541. The catalyst according to the present invention can be used in similar amounts and under similar conditions to known olefin polymerisation catalysts.
The supported catalyst compositions prepared according to the method of the present invention are particularly suitable for use in the gas phase.
The polymerisation may optionally be carried out in the presence of hydrogen. Hydrogen or other suitable chain transfer agents may be used to control the molecular weight of the produced polyolefin.
The present invention will now be further illustrated by reference to the following examples.